A method is provided for limiting the inflow of formation water during a well turn around to maximize polymer recovery after a hydraulic fracturing treatment of a formation. The method includes a step for selectively blocking the pore structure in a water-bearing zone and not blocking the pore structure of a hydrocarbon zone at the formation face; performing a hydraulic fracturing treatment using a fluid having a polymer; and turning the well around to recover the polymer. There is also provided a method of acidizing, preferably matrix acidizing, a formation having a hydrocarbon zone and a water-bearing zone. The method includes a step for selectively blocking the pore structure in the water-bearing zone at the formation face to selectively retard migration of acid into the water-bearing zone; and injecting acid into the formation, wherein the acid is diverted from the water-bearing zone to the hydrocarbon zone as a result of the selective blocking step. When the water-bearing zone contains a residual amount of hydrocarbon residues, the method further includes injecting a mutual solvent prior to the step for selectively blocking.
In these methods, the step for selectively blocking preferably forms a plug of a viscous fluid in the pore structure of the water-bearing zone at the formation face. The viscous fluid preferably has at least a viscoelastic surfactant capable of forming a worm-like micelle in an aqueous environment, a water-soluble salt to effect formation stability, and an aqueous carrier fluid.